— 374 — 



are about 10 cm. high, and consist of long branches, 160/i thick above, 

 which are furnished with short, unilaterally placed or alternating, about 

 65 ^ thick branchlets. The sporangia occur in terminal rows and their 

 openings are situated in the upper end. 



I have also with doubt referred to this species some plants, that I 

 met with at Flatey in the beginning of May. My plants were about 

 5 — 6 cm. high and consisted of a short, ISO/i thick main axis with long, 

 about 116/i thick branches, which were furnished with short and dense 

 branchlets, about 70^ thick. Possibly my specimens ought rather to be 

 referred to the next species. Fructiferous specimens have been gathered 

 by Strcimfelt in September. 



SW. I eel. Flatey. 



S. Icel. Eyrarbakki (Stromfelt). 



Cladophora sericea (Huds.) Aresch. Phyc. scand. p. 194. 



forma. 



I have in several places, especially in SW. Iceland and S. Iceland, 

 met with a small Cladophora growing in pools and rock-clefts at high- 

 water mark. These specimens, I think, are to be regarded as belonging 

 to the form-series of Cladophora sericea Aresch. My plants are usually 

 about 2 cm. high rarely higher, up to 6 cm. They usually grow rather 

 gregariously but plants growing solitarily also occur. They consist of a 

 short, 130 — 200;/ thick main axis with 90 — 190(— 260 //) thick longer 

 branches, bearing shorter or longer, more or less branched branchlets. 

 The upper branchlets are more or less secund on the one or the other 

 side of their axis, sometimes 1 have found them alternating or verticillate 

 towards the apex. The uppermost branchlets are not seldom somewhat 

 fasciculate. The cells are about 2 — 6 times longer than broad and usually 

 considerably thicker in the upper end especially in the lower part and in 

 the middle. The rhizoids are irregularly and repeatedly branched and 

 their apex is not rarely incurved. The cells of the rhizoids I have often 

 found containing large quantities of starch. The lower end of the main 

 axis seems to be destroyed gradually and most of the rhizoids of older 

 plants — 1 have not seen young plants with rhizoids — are produced 

 in the way that the cells of the lower part of the axis grow downwards 

 surrounded by the outer layers of the walls of the axis, which do not 

 partake in the growth; the rhizoids are thus in their first stage of deve- 

 lopment unbranched and intramatrical, but when they have reached out 

 of the surrounding mantle of the old cell walls they begin to branch 

 (cfr. C. gracilis fig. 19 a.). Rhizoids are also produced from the lower cells 

 of tiie branches, and I have thus not rarely seen two, parallel young 

 rhizoids growing downwards surrounded by the outer layers of the walls 



